The invention relates to a self-locking safety descender for descending along a rope, comprising:
a first fixed flange supporting a braking pad and a mobile pulley in the form of a cam, said pulley being mounted with limited rotation on a first articulation spindle between a locking position and an unlocking position, and separated from the pad by a space for passage of the rope, PA1 a second retractable flange, separated from the first flange by a transverse gap, and able to occupy a withdrawn position for fitting or removal of the rope, and a closed position, in which the rope is held captive in the space, PA1 an actuating handle of the pulley to perform manual unlocking of the rope, PA1 and a first spring to return the pulley to the unlocking position when the tension of the rope is lower than a preset threshold.
The document FR-A-2,451,752 refers to a self-locking descender having two possibilities of locking the rope depending on the spatial position of the actuating handle. The pulley is permanently securedly affixed to the handle and comprises for this purpose two angularly staggered bosses which alternately lock the rope against a fixed stud, depending on whether the handle is in a raised position or in a lowered position. Unlocking of the rope takes place in an intermediate position. The locking position is achieved following total release of the handle, resulting in rotation of the pulley due to the action of the tension of the rope and the clamping of the rope by the first boss. The second locking position results from the action of the second boss which clamps the rope against the fixed stud at a different place following maximum lowering of the handle. A permanent actuating force is however required on the handle in said lowered position to maintain this second locking of the rope. A decrease of the manual force on the handle, notably due to tiredness, may move the handle to the intermediate position, with a risk of unlocking the rope, which may jeopardize the safety of the person.